Carbon dioxide, labeled

A low level of carbon dioxide labeled with 14C is accidentally released into the atmosphere surrounding industrial workers as they resume work following the lunch hour. Unknowingly, they breathe the contaminated air for one hour. Which of the following compounds will be radioactively labeled ... 

The oxygen formed clearly comes from H20 and not from C02, because photosynthesis in the presence of water labeled with lgO produces oxygen labeled with 180, whereas carbon dioxide labeled with 180 does not give oxygen labeled with 180. Notice that the oxidation of the water produces two electrons, and that the formation of NADPH from NADP requires two electrons. These reactions occur at different locations within the chloroplasts and in the process of transferring electrons from the water oxidation site to the NADP reduction site, adenosine diphosphate (ADP) is converted to adenosine triphosphate (ATP see Section 15-5F for discussion of the importance of such phosphorylations). Thus electron transport between the two photoprocesses is coupled to phosphorylation. This process is called photophosphorylation (Figure 20-7). 

Carbon dioxide is required for the conversion of acetyl CoA into fatty acids. Yet when carbon dioxide labeled with is used, none of the labeled carbon appears in the fatty acids that are formed. How do you account for these facts ... 

For aerobic degradation, uptake of oxygen or the evolution of carbon dioxide (labeled or unlabeled) is most widely used. Use of the concentration of dissolved organic carbon may present technical problems when particulate matter is present, although analysis of dissolved inorganic carbon in a closed system has been advocated (Birch and Fletcher 1991) and may simultaneously overcome problems with poorly soluble or volatile compounds. 

Carbon dioxide, labelled with C, has been incorporated in the alpha acids during ripening (65). The presence of 4-deoxyhumulone or 2-(3-methylbutanoyl)-4,6-bis(3-methyl-2-butenyl)phloroglucinol (12, Rg. 13) in hops supports the view that the hop alpha acids and the hop beta acids are derived from this common precursor... 

If a plant is illuminated in a closed container the carbon dioxide concentration inside the container eventually reaches a steady level which is known as the carbon dioxide compensation point. The final level represents the balance attained between carbon dioxide fixing and carbon dioxide releasing reactions. That carbon dioxide releasing reactions do occur is readily demonstrated if leaves which have previously been photosynthesising in labelled carbon dioxide are transferred to unlabelled carbon dioxide—labelled carbon dioxide can be detected in the atmosphere surrounding the leaves. This sort of experiment underlines the fact that when photosynthesis is measured as CO2 uptake or oxygen evolution the value obtained represents apparent photosynthesis—the balance between reactions resulting in... 

Production and Shipment. Estimated adiponitrile production capacities in the U.S. in 1992 were about 625 thousand metric tons and worldwide capacity was in excess of lO metric tons. The DOT/IMO classification for adiponitrile is class 6.1 hazard, UN No. 2205. It requires a POISON label on all containers and is in packing group III. Approved materials of constmction for shipping, storage, and associated transportation equipment are carbon steel and type 316 stainless steel. Either centrifugal or positive displacement pumps may be used. Carbon dioxide or chemical-foam fire extinguishers should be used. There are no specifications for commercial adiponitrile. The typical composition is 99.5 wt % adiponitrile. Impurities that may be present depend on the method of manufacture, and thus, vary depending on the source. 

Synthetic chemical approaches to the preparation of carbon-14 labeled materials iavolve a number of basic building blocks prepared from barium [ CJ-carbonate (2). These are carbon [ C]-dioxide [ CJ-acetjlene [U— C]-ben2ene, where U = uniformly labeled [1- and 2- C]-sodium acetate, [ C]-methyl iodide, [ C]-methanol, sodium [ C]-cyanide, and [ CJ-urea. Many compHcated radiotracers are synthesized from these materials. Some examples are [l- C]-8,ll,14-eicosatrienoic acid [3435-80-1] inoxn. [ CJ-carbon dioxide, [ting-U— C]-phenyhsothiocyanate [77590-93-3] ftom [ " CJ-acetjlene, [7- " C]-norepinephrine [18155-53-8] from [l- " C]-acetic acid, [4- " C]-cholesterol [1976-77-8] from [ " CJ-methyl iodide, [l- " C]-glucose [4005-41-8] from sodium [ " C]-cyanide, and [2- " C]-uracil [626-07-3] [27017-27-2] from [ " C]-urea. All syntheses of the basic radioactive building blocks have been described (4). 

Even higher organisms can be used for the production of labeled compounds. Plants, tobacco, or Canna indica for example, when grown in an exclusive atmosphere of radioactive carbon dioxide, [ 002], utilize the labeled precursor as the sole source of carbon for photosynthesis. After a suitable period of growth, almost every carbon atom in the plant is radioactive. Thus, plants can serve as an available source of C-labeled carbohydrates (9). 

C-labeled carbon dioxide is administered to a green plant, and shortly thereafter the following compounds are isolated from the plant 3-phosphoglycerate, glucose, erythrose-4-phosphate, sedoheptulose-l,7-bisphosphate, ribose-5-phosphate. In which carbon atoms will radioactivity be found ... 

Alcohol sulfates are easily metabolized by mammals and fishes either by oral or intraperitoneal and intravenous administration. Several labeled 35S and 14C alcohol sulfates have been used to determine their metabolism in experiments with rats [336-340], dogs [339], swines [341], goldfish [342], and humans [339]. From all of these studies it can be concluded that alcohol sulfates are absorbed in the intestine of mammals and readily metabolized by to and p oxidation of the alkyl chain and excreted in the urine and feces, but are also partially exhaled as carbon dioxide. Fishes absorb alcohol sulfates through their gills and metabolize them in a similar way to that of mammals. 

Blanck H, Admrraal W, eleven REMJ, Guasch H, van den Hoop MAGT, Ivorra N, Nystrom B, Paulsson M, Petterson RP, Sabater S, Tubbing GMJ (2003) Variability in zinc tolerance, measured as incorporation of radio-labeled carbon dioxide and thymidine, in periphyton communities sampled from 15 European river stretches. Arch Environ Contam Toxicol 44 17... 

Phenyl radical, side by side with methyl radical, carbon dioxide and methyl benzoate, was also stabilized in an inert matrix as a product of UV photolysis of acetyl(benzoyl)peroxide [112] (Pacansky and Brown, 1983). Of nine IR bands of the radical C6H5, intense absorption at 710 cmwhich was shifted to 519 cm for the deuterium-labelled radical C Ds, has been assigned to out-of-plane CH deformation. The bands of the phenyl radical... 

Table VI summarizes the material presented in the previous discussion. It correlates the changes in oxygen and carbon dioxide partial pressures, showing the pathological causes for the imbalances. In addition, it contains the various diagnoses of acid-base abnormality (using same numbers as in Figures 1 and 2 and Table I). Considering the format of Table VI as a tic-tac-toe set-up, we can label the nine portions by the letters A-I for identification in Table VII which gives examples of various conditions associated with such blood gas abnormalities (20-30).

Root products, as defined by Uren and Reisenauer (17), represent a wide range of compounds. Only secretions are deemed to have a direct and immediate functional role in the rhizosphere. Carbon dioxide, although labeled an excretion, may play a role in rhizosphere processes such as hyphal elongation of vesicular-arbuscular mycorrhiza (39). Also, root-derived CO2 may have an effect on nonphotosynthetic fixation of CO2 by roots subject to P deficiency and thus contribute to exudation of large amounts of citrate and malate, as observed in white lupins (40). The amounts utilized are very small and, in any case, are extremely difficult to distinguish from endogenous CO2 derived from soil and rhizosphere respiration. 

The photodegradation of para-aramid in an 0 atmosphere allows the differentiation between the accelerated experimental photooxidative conditions from its usual daylight exposure effects. This study illustrated an estimation of the rates of photooxidation of a commercial para-aramid product (i.e., DuPont s Kevlar-29 woven fabric) based on the oxygen-18-labelled carbon dioxide ( CC and CC ) decarboxylated from the sample. The oxygen-18-labelled atoms, which are inserted in the macromolecules, were analyzed for the photodegradation processes. This technique also allows the radial l O-distribution measurement from the fiber surface toward the fiber center. 

The results of Ito et a/.101 indicate that careful experiments including enough blank experiments are necessary in studies of photoelectrochemical reduction products of carbon dioxide because, unfortunately, the products observed to date are in very low concentrations. Purification of the carbon dioxide gas itself should also be considered, expecially in experiments in which a continuous flow of C02 gas is used. Accumulation of organics which are present as impurities in C02 gas is often observed. Purification methods for C02 gas used are given in some papers,95"97,102 but establishment of a common recommended method would be helpful. Also, it may be advisable to reexamine earlier work on C02 reduction to exclude meaningless results. In future experiments, the use of labeled 13C02 is to be recommended. 

A bottle labelled as 12% acid in aqueous methanol, and probably two years forgotten, exploded in storage, breaking adjacent bottles[l]. Trichloracetic acid is known to be more unstable, with respect to carbon dioxide and chloroform, in aqueous solution than pure. The reaction usually requires either heat or base catalysis [2], Storage of trichloroacetic acid at less than 30% concentration is not advised [3], Hydrolysis of the trichlorogroup is also conceivable, which would yield intermediate oxalyl monochloride, which habitually breaks down to give carbon monoxide, dioxide and hydrogen chloride. 

Studies using labeled oxygen have shown that oxygen evolved during the reaction is a product of water oxidation and is not derived from carbon dioxide. The overall reaction of synthesis of glucose (C6H1206) can be written as [8,37,113,114]... 

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